Technical Field
The present disclosure relates to a stator structure including coil covers and, more particularly, to a stator structure suitable for a resolver and the resolver.
Background
A resolver is known as a rotation angle sensor. For example, the resolver is configured from a stator core including a plurality of teeth sections extending from an annular yoke section toward the center on the inner circumference side and a rotor disposed to be opposed to the teeth sections of a stator on the inner side of the stator core. Winding wires are wound around the teeth sections via an insulator to form coils. The winding wire is configured by an excitation winding wire for inputting an excitation signal and two detection winding wires for outputting two-phase signals according to a rotation angle of the rotor. A sine signal depending on sin θ and a cosine signal depending on cos θ are respectively output from the detection winding wires. In the resolver, there is known a configuration in which two coil covers for covering the winding wires (the coils) are attached to both sides of the stator core (see, for example, Japanese Patent Application Laid-Open No. 2009-148081).
In the configuration disclosed in Japanese Patent Application Laid-Open No. 2009-148081, as shown in FIG. 7 and the like of Japanese Patent Application Laid-Open No. 2009-148081, a plurality of first column sections and a plurality of first receiving sections are provided in a first coil cover and a plurality of second column sections and a plurality of second receiving sections are provided in a second coil cover. The first and second column sections respectively extend to spaces (slots) among the teeth in which the insulator is provided. After the first and second coil covers are attached to the stator core, ultrasonic vibration is applied to positions where the second receiving sections of the second coil cover are provided. The first column sections of the first coil cover and the second receiving sections of the second coil cover are welded to each other. Consequently, the first and second coil covers are coupled to each other.
On the other hand, as the configuration in which the two coil covers are coupled to each other, there is known a configuration in which snap-fit by locking protrusion bodies and locking step sections is used (see, for example, Japanese Patent Application Laid-Open No. 2004-135402).
In a stator structure for a resolver disclosed in Japanese Patent Application Laid-Open No. 2004-135402, protrusion bodies for locking provided in a first coil cover pierce through slots among teeth in which an insulator is provided and engage with cylindrical protrusion bodies provided in a second coil cover, whereby the two coil covers are coupled. At this point, after locking claws of the protrusion bodies for locking engage with and pierce through ring-like taper sections of the cylindrical protrusion bodies while involving deformation or distortion due to expanding slots, the locking claws are locked to locking step sections on the rear side of the cylindrical protrusion bodies by snap-fit.
Incidentally, in order to realize high reliability in a stator of a resolver, it is necessary to prevent or suppress foreign matter from reaching coils from the inner circumference side of the stator. In order to realize the high reliability, there is a method of providing a protection structure for covering openings of slots with respect to the inner circumference side of the stator. Such a protection structure can also be realized by, for example, the column sections and the receiving sections or the protrusion bodies locking to each other described in Japanese Patent Application Laid-Open No. 2009-148081 and Japanese Patent Application Laid-Open No. 2004-135402 described above.
However, since the column sections and the receiving sections or the protrusion bodies described in Japanese Patent Application Laid-Open No. 2009-148081 and Japanese Patent Application Laid-Open No. 2004-135402 are also used as a structure for coupling the two coil covers, a positional relation between the column sections and the receiving sections or the protrusion bodies is fixed by welding or locking during attachment of the coil covers. Therefore, if errors from design occur in the positions and the sizes of the column sections and the receiving sections or the protrusion bodies because of manufacturing variation of the coil covers or the like, when the welding or the locking is performed, errors sometimes appear as distortions of the shape of the protection structure. Possibility of occurrence and a degree of such distortion increase as the numbers of the column sections and the receiving sections or the protrusion bodies increase. In this case, it is likely that an unintended gap will be formed by the distortion of the protection structure and that foreign matter will intrude into the slots from the gap. At this point, depending on the size of the intruding foreign matter, the foreign matter is likely to close spaces among a plurality of terminals to which the ends of the winding wires configuring the coils are bound to electrically connect the coils to the outside. When the foreign matter closing the spaces among the terminals is made of metal, the terminals electrically short-circuit. Consequently, the reliability of the resolver is likely to deteriorate.